Refrigerant tube for a heat exchanger

Details Refrigerant tube for a heat exchanger Refrigerant tube for a heat exchanger

1999-06-25

2001-06-19

Lateef, Marvin M. (Department: 3743)

Heat exchange

Tubular structure

With discrete heat transfer means

C165S177000

Reexamination Certificate

active

06247529

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to heat exchangers, and more specifically to refrigerant tubes for a heat exchanger.
2. Disclosure Information
FIGS. 1-2
illustrate the typical construction of most heat exchanger refrigerant tubes according to the prior art. As typified in
FIG. 2
, this construction includes a flat metallic tube
10
having flat upper and lower walls
12
/
14
with a plurality of reinforcing walls
16
connected between the upper and lower walls. These reinforcing walls
16
extend parallel to each other along the length of the tube
10
, thereby forming a plurality of parallel flow channels
17
each bounded by the upper and lower walls
12
/
14
and two reinforcing walls
16
. This tube construction can be made using a variety of approaches, such as those disclosed in U.S. Pat. No. 5,638,897 to Hirano et al., U.S. Pat. No. 5,784,776 to Saito et al., and U.S. Pat. No. 5,799,727 to Liu (each of which being incorporated herein by reference).
Such refrigerant tubes can be generally grouped into two categories: discrete flow and non-discrete flow. Discrete flow refrigerant tubes have parallel flow channels
17
which do not communicate with one another along the length of the tube; as illustrated in
FIG. 3A
, the reinforcing walls
16
of discrete flow tubes completely segregate each flow channel
17
from its neighboring flow channels. Non-discrete flow tubes, on the other hand, provide a plurality of apertures or openings
18
in the reinforcing walls
16
, as illustrated in
FIG. 3B
; these openings
18
permit fluid communication among adjacent flow channels
17
. Non-discrete flow tubes are more difficult to manufacture, but have the advantage of providing better heat transfer because of the cross-flow of refrigerant fluid among the flow channels through the openings
18
.
Although it is known to provide such openings
18
to facilitate fluid cross-flow, no guidance has heretofore been provided for designing the size and spacing of these openings so as to optimize the heat transfer potential of non-discrete flow refrigerant tubes.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of the prior art approaches by providing a non-discrete flow refrigerant tube for a heat exchanger wherein the cross-flow among adjacent flow channels provides optimized heat transfer characteristics. The refrigerant tube comprises: a generally flat tube having generally flat upper and lower walls; a plurality of reinforcing walls connected between the upper and lower walls, the reinforcing walls extending along and generally parallel with a longitudinal axis of the tube and being spaced apart from one another by a predetermined distance; and a plurality of communication holes distributed along the length of each reinforcing wall, thereby defining a plurality of discrete wall portions along each reinforcing wall, each of the discrete wall portions being disposed between adjacent communication holes and having an upstream edge and a downstream edge thereof, the communication holes and discrete wall portions having lengths L
1
and L
2
, respectively, as measured along the longitudinal axis, the communication holes being spaced apart along each reinforcing wall by a pitch P. Each communication hole in each reinforcing wall is disposed between the upstream and downstream edges of a laterally adjacent discrete wall portion of each adjacent reinforcing wall, such that a wall overlap ratio Wr, defined as [P−2L
1
]/P, is greater than 0, and preferably 0.4≦Wr≦0.6.
It is an object and advantage that the present invention provides an optimized range for the relative size and spacing of communication holes and discrete wall portions of non-discrete flow refrigerant tubes, such that the overall heat transfer coefficient of such tubes is optimized.
Another advantage is that the present invention may be easily integrated into the manufacturing process for known refrigerant tubes.
Yet another advantage is that the optimized design of the present invention may be used equally well with either one-piece or two-piece refrigerant tube constructions.
These and other advantages, features and objects of the invention will become apparent from the drawings, detailed description and claims which follow.


REFERENCES:
patent: 5323851 (1994-06-01), Abraham
patent: 5553377 (1996-09-01), Hirano et al.
patent: 5638897 (1997-06-01), Hirano et al.
patent: 5689881 (1997-11-01), Kato
patent: 5730215 (1998-03-01), Hirano et al.
patent: 5749144 (1998-05-01), Hirano et al.
patent: 5784776 (1998-07-01), Saito et al.
patent: 5799727 (1998-09-01), Liu
patent: 5931226 (1999-08-01), Hirano et al.
patent: 0617250A2 (1993-03-01), None

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